Secretary of Defense Ash Carter used the Pentagon podium Thursday to stump for support for the idea of setting up a “Guantánamo North,” emphasizing closure by transferring the last war-on-terror prisoners to the U.S. over the dozens of detainees already approved for release from U.S. military custody.

“As long as this detention facility remains open, it will remain a rallying cry for jihadi propaganda,” Carter told reporters at a news conference, adding that he ordered a recent site survey at Fort Leavenworth, Kansas, and Charleston, South Carolina, to gather information but not necessarily target those two military prisons as relocation sites.

“We will also be assessing other locations in coming weeks,” he said, without specifying which sites.

Carter said he and President Barack Obama agree on the need to close the detention center during this administration, saying taxpayers are “paying too high a price” for the detention center —which currently houses 116 captives maintained by a staff of 2,000 troops and contractors.

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A 2013 tally estimated the U.S. had spent more than $5 billion there and, based on that soup-to-nuts crunch currently spends more than $3 million a year per prisoner there. “It’s expensive for this department and not something that the president wants to leave for his successor,” Carter said.

Of the remaining 116 prisoners, 52 are cleared for release to foreign countries with security agreements. But some captives, he said, remain as Law of War prisoners — indefinite detainees, or “forever prisoners” as they are known — and closure would require moving them to custody on U.S. soil. His staff is working on a “responsible, realistic and security focused plan for an alternative detention facility in the United States,” which would require Congress lifting its ban on the transfer of Guantánamo detainees to anywhere in the United States for any reason.

Carter defended the slow pace of detainee releases. Just six captives have been transferred since Carter took office in February — long-cleared Yemeni men who went to Oman on a deal arranged before his tenure — and only one more transfer is expected this summer.

“I’ve approved the transfer of several detainees and will continue to do so when appropriate,” Carter said.

He said each transfer requires “complicated negotiations with international partners, extensive consultations with leaders of national security and legal organizations and final approval by me. We do this carefully. We do it deliberately.”